I've searched and searched for this info. in books and on the internet
and I just can't find anything on the 12 string guitar as far as tuning
and frequencies and such.
Because so many people have requested help in this area, I decided to
make my own 12 string guitar tuners. I borrowed the picture
from my Tip 28 and tuned my 12 string guitar with a chromatic tuner and
recorded the notes into easy to play MP3, Real Audio, or Windows Media files for you to listen to to tune your 12 string
guitar. Just click on the knobs and listen to the pitches.

It's much the same as a 6 string guitar E A D G B E low to high except
the 4 lowest pairs of strings are tuned an octave apart. Be careful, not all 12 string guitars
(especially old ones) are designed to be tuned up to this pitch. Some
have to be tuned a note or two lower. Caution:
There are a few rare cases where
you may buy a 12 string guitar and it will be strung differently than
this. Make sure the thinner high octave strings are in the
same positions
as pictured below. In some rare cases they will be switched
from a
manufacturer.